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Diffstat (limited to 'tests/ui/traits/new-solver/canonical-ty-var-eq-in-response.rs')
-rw-r--r-- | tests/ui/traits/new-solver/canonical-ty-var-eq-in-response.rs | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/tests/ui/traits/new-solver/canonical-ty-var-eq-in-response.rs b/tests/ui/traits/new-solver/canonical-ty-var-eq-in-response.rs new file mode 100644 index 000000000..d1c6b1077 --- /dev/null +++ b/tests/ui/traits/new-solver/canonical-ty-var-eq-in-response.rs @@ -0,0 +1,39 @@ +// check-pass +// compile-flags: -Ztrait-solver=next + +trait Mirror { + type Item; +} + +struct Wrapper<T>(T); +impl<T> Mirror for Wrapper<T> { + type Item = T; +} + +fn mirror<T>() +where + Wrapper<T>: Mirror<Item = i32>, +{ +} + +fn main() { + mirror::<_ /* ?0 */>(); + + // Solving `<Wrapper<?0> as Mirror>::Item = i32` + + // First, we replace the term with a fresh infer var: + // `<Wrapper<?0> as Mirror>::Item = ?1` + + // We select the impl candidate on line #6, which leads us to learn that + // `?0 == ?1`. + + // That should be reflected in our canonical response, which should have + // `^0 = ^0, ^1 = ^0` + // !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! + // !! We used to return a totally unconstrained response here :< !! + // !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! + + // Then, during the "equate term" part of the projection solving, we + // instantiate the response from the unconstrained projection predicate, + // and equate `?0 == i32`. +} |